Space shuttle fuel cells

Stoichiometry has important practical applications, such as predicting how much product can be formed in a reaction. For example, in the space shuttle fuel cell, oxygen reacts with hydrogen to produce water, which is used for life support (Fig. L.l). Let s look at the calculation space shuttle engineers would have to do to find out how much water is formed when 0.25 mol 02 reacts with hydrogen gas. 

Fuel cells deliver as much power as batteries weighing ten times as much. On a typical seven-day mission, the space shuttle fuel cells consumed 1500 pounds of hydrogen and generated 190 gallons of water. 

Typical polarization curves for alkaline fuel cells are shown in Fig, 27-63, It is apparent that the all aline fuel cell can operate at about 0,9 and 5()() rnA/cnr current density. This corresponds to an energy conversion efficiency of about 60 percent IIII, The space shuttle orbiter powder module consists of three separate units, each measuring 0,35 by 0,38 by I rn (14 by 15 by 40 in), weighing 119 kg (262 lb), and generating 15 kW of powder. The powder density is about 100 W/L and the specific powder, 100 W/kg,... 

FIGURE L.l One of the three hydrogen-oxygen fuel cells used on the space shuttle to provide life-support electricity and drinking water. 

Self-Test 4.12B The reaction of H2 and 02 gases to produce liquid H20 is used in fuel cells on the space shuttles to provide electricity. What mass of water is produced in the reaction of 100.0 L of oxygen stored at 25°C and 1.00 atm ... 

The problem was solved by Francis Bacon, a British scientist and engineer, who developed an idea proposed by Sir William Grove in 18.39. A fuel cell generates electricity directly from a chemical reaction, as in a battery, but uses reactants that are supplied continuously, as in an engine. A fuel cell that runs on hydrogen and oxygen is currently installed on the space shuttle (see Fig. L.l). An advantage of this fuel cell is that the only product of the cell reaction, water, can be used for life support. 

The hydrogen-oxygen cell used in the space shuttle is called an alkali fuel cell, because it has an alkaline electrolyte ... 

Alkaline fuel cells (AFCs). The electrolyte is 40 to 70% KOH, the working temperatures are 60 to 240°C. Such systems were used in the spacecraft of the Apollo program and in the U.S. space shuttle. 

After it has been separated, hydrogen is an unusually clean-energy carrier and clean enough for the U.S. space shuttle program to use hydrogen-powered fuel cells to operate the shuttle s electrical systems while the by-product of drinking water is used by the crew. 

The space shuttle uses a fuel cell as a source of energy. This cell depends on the oxidation of hydrogen by oxygen to form water. The fuel cell operates under basic conditions, so it is sometimes referred to as an alkaline fuel cell. Figure 11.31, on the next page, shows the design of the cell. The half-reactions and the overall reaction are as follows. 

Alkaline fuel cell (AFC) working at 80 °C with concentrated potassium hydroxide as electrolyte, conducting by the OH anion. This kind of fuel cell, developed by IFC (USA), is now used in space shuttles. 

Fuel cells have also been used for Skylab, a space station launched on May 14, 1973, and in orbit for more than six years, as well as in the space shuttles. Other uses for these reliable devices include providing electricity at remote facilities that are beyond the reach of power lines, and as back-up generators at hospitals, which cannot afford to lose power for any length of time. 

NASA laimches the first space shuttle, which is equipped with fuel cells. 

Space shuttle orbiter -fuel cells for [FUEL CELLS] (Vol 11)... 

FIGURE L.l One of the three hydrogen-oxygen fuel cells used on the space shuttle. Although only one cell is needed to provide life-support electricity and drinking water shuttle flight rules require that all three be functioning. In April 1987, a mission of space shuttle Columbia was cut short when one of the fuel cells malfunctioned. 

Figure 6.24 The space shuttle s computers use electricity produced by fuel cells.

Fuel cells have been reliably providing electricity to spacecraft since the 1960s, including the Gemini and Apollo missions as well as the space shuttle. The leading manufacturer of fuel cells for the National Aeronautics and Space Administration (nasa), United Technologies Corporation, has sold commercial units for stationary power since the early 1990s, with more than 200 units in service. 

Fig. 13.17. Performance of advanced lightweight pressurized alkaline fuel cells. The dashed lines show initial advanced AFC cell results. A, 149 °C, 17 bar B, 140 °C, 17 bar C, 127 °C, 17 bar D, 110 °C, 4 bar E, 82°C, 4 bar F, 82 °C, 1 bar G, 0.2 MgPt-C and the same conditions as F (IR-free) H, 10 mg/cm2 Au/Pt, 127 °C, 1 bar (IR-free). , nominal performance of space shuttle cell (1000 h) , United Technologies target goal (1000 hr). Solid lines show solid polymer electrolyte cells for comparison under different pressure and temperature conditions. (Reprinted from Assessment of Research Needs for Advanced Fuel Cells, S. S. Penner, ed., Pergamon Press, 1986, pp. 14,87.)...

NASA has long used liquid hydrogen to fuel space rockets. Now NASA also uses fuel cells within the space shuttle cabin to provide electrical power to the shuttle s instruments. The water that is created in the fuel cell is then used as drinking water by the crew. 

Workers take apart a fuel cell that has been removed from the space shuttle. 

The application of gold as an electrocatalytic component within the fuel cell itself has to date been limited primarily to the historical use of a gold-platinum electrocatalyst for oxygen reduction in the Space Shuttle/Orbiter alkaline fuel cells (AFC)88 and the recent use of gold for borohydride oxidation in the direct borohydride alkaline fuel cell (DBAFC).89,90 Electrocatalysts with lower cost, improved carbon monoxide tolerance and higher... 

Alkaline fuel cells (AFCs) were the first type of fuel cell to be widely used in space exploration applications-for example, in NASA s Apollo and space shuttle flights. Figure 1.8 shows a schematic of an AFC stmcture. AFCs use H2 and 02 as fuel and oxidant, respectively. The electrolyte is a concentrated KOH solution absorbed into an asbestos matrix. The temperature for AFCs ranges from 100-250°C and the efficiency can be > 60%. OH ions are transported through the electrolyte from cathode to anode. The reactions are as follows ... 

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